1. Field of the Invention
This invention relates to methods and systems for high-speed, precise micromachining of an array of devices. This invention also relates to the field of resistor trimming, particularly trimming of serpentine resistors on thin film block structures. Laser resistor trimming involves laser-processing cuts in an area of resistive material between conductors.
2. Background Art
Resistor trimming (as well as trimming and micro-machining of other electronic components and circuits) has evolved over the laser 20 years and is now used for adjusting circuits for thick film, thin film, and other electronic technologies. The publication “Trimming,” LIA HANDBOOK OF LASER MATERIALS PROCESSING, Chapter 17, pages 583-588, 2001 contains contributions describing several aspects of laser trimming. FIGS. 1a-1c of the present application are incorporated from the publication. FIG. 1a illustrates current flow lines of an untrimmed resistor, whereas FIG. 1b illustrates an effect of laser trimming on the current flow lines. FIG. 1c summarizes several results (stability, speed, and tolerances) with various resistor geometries and cut types.
The following exemplary U.S. patents are related to laser trimming methods and systems: 6,510,605; 6,322,711; 5,796,392; 4,901,052; 4,853,671; 4,647,899; 4,511,607; and 4,429,298.
U.S. Pat. No. 4,429,298 relates to many aspects of serpentine trimming. Basically, a serpentine resistor is formed with sequential plunge cuts and a final trim cut is made parallel to the resistor edge from the last plunge. It describes “progressively” making plunge cuts on a resistor alternately from one end, considers maximum and minimum plunge cut lengths, a resistance threshold of the plunge cuts for the trim cut, a faster cutting speed for plunge cuts, and a structured process flow with various resistance and cut length tests.
There is a continuing need for improved high-speed, micromachining such as precise trimming at all scales of operation, ranging from thick film circuits to wafer trimming.